What is the fermi level for exterensic semiconductors?
An extrinsic semiconductor is an intrinsic semiconductor doped with either electron donors or electron acceptors which will increase the electron or hole concentrations respectively. For an intrinsic semiconductor, the Fermi Energy level sits roughly at midpoint of the bandgap, if the effective mass of holes and electrons is the same. When the semiconductor is doped, the Fermi level moves either towards the conduction band if the doping is an electron donor or towards the valence band if the doping is an electron acceptor. For non-degenerate doping, the Fermi Level is given by Ef – Ei = kT ln(Nd/ni) for donor doping Ei – Ef = kT ln(Na/ni) for acceptor doping where Na, Nd are the acceptor/donor concentrations, ni is the intrinsic carrier concentration, kT is the thermal energy, and Ei is given by Ei = Emid + 3/4 kT ln (mp/mn) where Emid is the energy at mid band-gap, mp and mn are the effective masses for holes and electrons respectively. When the semiconductor is highly doped, the ferm
